Napoli have dropped into the competition after elimination from the Champions League.
“It was definitely a disappointment," Koulibaly admitted, speaking to El Heddaf TV.
“It's a competition everyone wants to play in and an important showcase. Now we're in the Europa League and we're playing to win it, we're always competitive and we want to achieve this goal.
“The Scudetto? It's better not to speak because we're very superstitious in Naples, obviously we'll wait and see what the pitch says toward May both for the Europa League and the Scudetto."